At the moment all of the users are on the same class C subnet which, including the addresses used by the servers, is quite congested as you might imagine. My proposal is to introduce a router and create 3 VLANs on the switches; leave the servers on the current subnet to minimise reconfiguration of firewall rules and so on and transfer the users to the two other VLANs spread across the switches. The router would be responsible for getting data between the VLANs.

My questions are:

Would I need a 3 interface router? Or can I use one with less interfaces and just plug it into a trunk port on one or two of the VLANs and have the switches send the packets to the correct switch in the stack? Would 2950 switches be fast enough for this configuration?

If a 3 legged router is best, would it be sensible to get a 2 interface model and add another NIC? I haven't found many with 3 10/100/1000 NICs.

This isn't a big environment, but it's not tiny either. I'm looking for some space to expand too in the future. What series of Cisco routers should I be looking at? I've looked at the 2700 and 3800 series' so far.

Having read a bit more I see that most if not all Cisco routers support 802.1q VLANs, meaning that potentially I could use a router with less physical interfaces than the number of VLANs. I guess though that I'll run into a problem running all that traffic through one interface, as the users are now used to a solely switched network, and would probably perceive this upgrade as a "downgrade"!

You're on the right track, but you might want to consider a layer 3 switch instead. An L3 switch has all the basic routing capabilities of a router (minus some advanced stuff) to route VLAN "flows" at full wire speed.
With a router using vlan tagged sub-interfaces - yes you will create an artificial bottleneck in the network by trying to use it.
Something like Cisco's 3560 switch working as the backbone switch with all 2950's attached to it directly if you can. You can get the gigabit model and assuming the 2950's have gigabit uplinks, you can create a full gig backbone. http://www.cisco.com/en/US/products/hw/switches/ps5528/index.html

Learn about Hyper-V features that increase functionality and usability of Microsoft Windows Server 2016. Also, throughout this eBook, you’ll find some basic PowerShell examples that will help you leverage the scripts in your environments!

A decent L3 switch is less $ than a 3800 series router
The 3560 doesn't really "control" the other switches, just the VLAN's and the layer 3 routing between the vlans. It works best as a hub (as in hub-and-spoke) device with all the other switches hanging off of it.

Thanks to you both. The customer has many many issues which need to be addressed so I think this one might get sidelined for a little while, but I think either a L3 switch might be the way forward. I do intend to put in 100-150 users per VLAN and add space for growth as the company has seen rapid growth in the last few years.

Configuring network clients can be a chore, especially if there are a large number of them or a lot of itinerant users. DHCP dynamically manages this process, much to the relief of users and administrators alike!

Data center, now-a-days, is referred as the home of all the advanced technologies. In-fact, most of the businesses are now establishing their entire organizational structure around the IT capabilities.

Viewers will learn how to properly install and use Secure Shell (SSH) to work on projects or homework remotely.
Download Secure Shell:
Follow basic installation instructions:
Open Secure Shell and use "Quick Connect" to enter credentials includi…